Breathing sensor

ABSTRACT

A breathing sensor, adapted to be attached to a conduit between a source of breathing gas and an animal, said sensor comprising a substantially vertical conduit having a float therein which is movable in response to breathing of the animal, a sensor for detecting the motion of the float and for actuating, preferably, an audio signal.

United States Patent [191 Matson June 18, 1974 BREATHING SENSOR [76]Inventor: Louis R. Matson, 2961 25th St.,

Sacramento, Calif. 95818 [22] Filed: Oct. 4, 1973 [21] Appl. No.:403,678

Related U.S. Application Data '[63] Continuation-impart of Ser. No.290,340, Sept. 19,

1972, abandoned.

[52] U.S. C1 128/2 R, 128/208, 128/208, 73/240, 272/57 [51] Int. Cl A61b5/08 [58] Field of Search 128/2 R, 2 C, 2.08, 239, 128/208; 73/240;272/57 [56] References Cited UNITED STATES PATENTS 10/1967 Kohrer 128/2R 3,512,521 5/1970 Jones 128/208 3,635,214 1/1972 Rand 128/208 3,695,60810/1972 Hanson 128/208 X Primary Examiner-Aldrich F. Medbery Attorney,Agent, or FirmErnest L. Brown 1 5 1 ABSTRACT A breathing sensor, adaptedto be attached to a conduit between a source of breathing gas and ananimal, said sensor comprising a substantially vertical conduit having afloat therein which is movable in response to breathing of the animal, asensor for detecting the motion of the float and for actuating,preferably, an audio signal.

10 Claims, 10 Drawing Figures ELBZTEONS C IKUIT SIGNAL DEVlCE L asBREATHING SENSOR BACKGROUND OF THE INVENTION 1 This application is aContinuation in Part of U.S. Pat. application Ser. No. 290,340 which wasfiled Sept. 19, 1972, by Louis R. Matson, and now abandoned.

This invention pertains to a breathing sensor, particularly useful byveterinarians, for sensing the breathing of animals who are underanaesthesia.

A typical veterinarian performing surgery, unlike a medical doctor,frequently works alone and has to be away from his patient from time totime to answer a telephone or meet the owner of another animal. Whileaway from the animal which is under anaesthesia, it is desirable thatthe veterinarian have a continuous monitor on the breathing of thepatient.

It is instructive to consider various United States patents whichrepresent the state of the art.

The closest apparatus found by the inventor wasthat taught and shown inUS. Pat. No. 3,635,214 which issued Jan. 18, 1972 to William A. Rand,et. al. for a Visual Pulmonary Meter." The apparatus is a hollowcylindrical chamber for slidably receiving an apertured piston whichalso functions as a damper. A patient blows into one end of the chamberand the other end has a calibrated exit regulator for selectivelyvarying the rate at which air can escape from the chamber. The piston iseffectively in series between the operator and his source of breathinggas (the atmosphere).

US. Pat. Nos. 3,028,761 and 3,347,222 each pertain to a balloon orbellows arrangement wherein the bellows or balloon positions aremonitored by a photoelectric apparatus.

US. Pat. No. 3,605,729 teaches a vane which move in response tobreathing of a person, together with sensors for sensing the motion ofthe vane.

BRIEF DESCRIPTION OF THE INVENTION The apparatus contemplated by thisinvention uses means forming a substantially vertical cylindricalchamber, one end of which is connected to a conduit between a gas sourceand an animal. The other end of the chamber opens substantially toatmospheric pressure. In one embodiment that other end of the chamberopens into a complaint balloon. In another embodiment that other endopens into the atmosphere. Within the vertical cylindrical chamber is aspherical float which is preferably made of light weight nonhydrophilicmaterial such as styrofoam. As the animal breathes, the pressure in theconduit between the gas source and the animal varies. As that pressurevaries, the float moves up and down between two stops. A photo-sensor isused to determine when the float is at its bottom stop position, and thephoto-sensor is used to produce, preferably, an aural signal indicativeof the breathing of the animal.

The real virtue of this device is its extreme sensitivity, for to be aneffective small animal breathing monitor, it should be triggered by aforce as small as the force generated by breathing of a small cat underanaesthesla.

It is therefore an object of this invention to sense the breathing of ananimal.

It is a more specific object of this invention to provide an apparatuswhich is adapted to sense variations in breathing pressure in abreathing conduit which is BRIEF DESCRIPTION OF THE DRAWINGS Otherobjects will become apparent from the following description, takentogether with the accompanying drawings, in which:

FIG. 1 is a schematic view of a first embodiment of the conduits orpiping used to deliver breathing gas from a gas source to an animal,showing the apparatus of this invention connected between the breathingconduit and a flexible balloon;

FIG. 2 is a schematic view of a second embodiment of the conduits orpiping used to deliver breathing gas from a gas source to an animal,showing the apparatus of this invention connected between the breathingconduit from one component of the breathing gas and the atmosphere;

FIG. 3 is a view, partly in section, of a typical em bodiment of thesensor of this invention;

FIG. 4 is a view taken at 4-4 in FIG. 3;

FIG. 5 is a view, partly in section, taken at 5-5 in FIG. 3;

FIG. 6 is a view taken at 6-6 in FIG. 3;

FIG. 7 is a view, partly in section, of a second embodiment of thesensor of this invention;

FIG. 8 is a view, partly in section, taken at 8-8 in FIG. 7;

FIG. 9 is a typical electronic circuit used with the photosensors in thebreathing sensor of this invention, and

FIG. 10 is a graph of experimentally determined instrument size for astyrofoam float showing the preferred range of the inside diameter ofthe cylindrical chamber of this invention plotted against the floatweight.

DETAILED DESCRIPTION OF THE INVENTION In FIGS. 1 and 2, breathing gas ischanneled, during anaesthesia, from an oxygen source 10 and a nitrousoxide source 12 through conduits 14,16 into a mixing' chamber 18 andthence, through breathing conduit 20, to a throat catheter 22 which isinserted into the throat of an animal 24. Other anaesthetic gases may beused, as desired.

A sensor conduit 26 is attached either to breathing conduit 16 orbreathing conduit 20 to receive gas pressure from the breathing conduitand to carry gas to the apparatus 28 of this invention.

The apparatus 28 comprises a substantially vertical cylindrical element30, shown schematically in FIGS. 1 and 2 and in detail in FIGS. 3-8. Afloat 32 (FIGS. 3-7) is free to move up and down within the element 30,and its position is sensed, for example, by a photo-sensor 34 whichcooperates with an electronic circuit 36 to activate a signal device 38.A typical electronic circuit 36 and signal. device 38 is shown in FIG.9.

The preferred shape of the float 32 is spherical, and the preferredmaterial of the float is styrofoam. Experiments have shown, as set forthin FIG. 10, that spherical styrofoam floats weighing between 3 and 20milligrams positioned in cylindrical chamber 30 whose inside diameter isapproximately 1 millimeter greater than the float diameter are preferredfor a normal range of animals. The lightest weight float used was 3milligrams. Lighter floats are affected by static electricity whichcauses them to stick to the chamber glass.

The preferred inside diameter of the cylindrical tube for a 3 milligramfloat, having a density of 0.034 g/cc, is 6 millimeters. With thosedimensions, the breathing of an 8 weeks old kitten can easily bedetected. The maximum weight of the float which produces usable signalswith a 0.034 g/cc spherical styrofoam float is 20 milligrams. anythingheavier than 20 milligrams does not move sufficiently to produce auseable signal. With the 20 milligram float, the inside diameter of thecylindrical element 30 would need to be at least 12 millimeters.

The bottom line of the graph determines the minimum inside diameter forthe cylindrical element 30 to cause proper functioning of the apparatus.Anything less than the diameter specified by that line would cause undueinterference between the float and the inside diameter of the element30. If the inside diameter of the element 30 is increased above thediameter specitied by the bottom graph of FIG. 10, it should not beincreased more than one-sixth for proper operation of the apparatus. Ifit is increased more than onesixth, it is found that the float tends towander and there is excessive gas leakage around the float.

I have found that the optimum combination for best function of theapparatus for use by veterinarians in ordinary practice wherein the mostsensitive breathing is that of a small kitten about 8 weeks old, is thatshown in FIG. at l l milligrams with an inside diameter of thecylindrical chamber 30 preferably at 9 millimeters but ranging up to 10and /2 millimeters. With that optimum sized spherical styrofoam float, afull range of breathing sensitivity for all animals normally appearingin a veterinarians office, and also including human beings, may besensed.

Note that with a spherical styrofoam float, the minimum inside diameterof the cylindrical member 30 varies with the weight of the sphericalfloat between 6 and 12 millimeters as the weight varies between 3 andmilligrams. This represents a clearance of approximately /a millimeterbetween the ball float and the glass chamber.

The bottom opening of the sensor cylindrical element may either be opento the atmosphere as shown in FIG. 2 or connected to a pliable balloon40, to conserve gas, as shown in FIG. 1.

The details of the apparatus 28 are shown in FIGS. 3-8. A substantiallyvertical cylindrical member 30 is connected into the sensor conduit 26with the bottom of the cylindrical member 30, typically, connected tosubstantially atmospheric pressure.

A float member 32, which is substantially spherical, is positionedwithin the cylindrical member 30 with clearance for free movement of thefloat member 32. The float member, preferably is made of styrofoam. Itmay, of course,'be made of other light weight material which will floatup and down as the pressure varies at the top of the cylindrical member30. The float material 32 should preferably be nonhydrophilic so thatmoisture in the gas does not increase the weight of the float.

The float member 32 is constrained to operate between a pair of stops42,44 (FIGS. 3-6). In the embodiment of FIGS. 3-6, the upperstop 42 is awire element which clamps over the upper lip of the cylindrical element30 as shown at 46,48.The lower stop 44 is a twisted wire element whichclamps over the lower lip of the cylindrical element 30 as shown at 50,52.

An alternative for the upper and lower stops 42,44, is shown in FIGS.7-8. A pin protrudes into the cylindrical member 30. The pin 60 hasscrew threads 62 thereon which screw into a plug member 64 which plugslike a stopper into the cylindrical member 30. The plug or stopper 64has ports 66 therein for the free flow of gas. A thumb screw 68 isattached to the screw 62 to adjust the position of the pedestal or stop60.

A light source 70 is positioned to direct illumination through the wallsof the cylindrical member 30 into the photo-sensor 34. To that end thewalls of the cylindrical member 30 are preferably of transparentmaterial such as glass. At least the region 72 of the cylindrical member30 must be transparent to channel illumination from the source 70 to thesensor 34. When the float 32 is positioned upon the lower stop 44 or 60,the float blocks the flow of illumination from the source 70 to thesensor 34 which then, through its associated electronics 36 eitheractivates or stops the signal device 38.

If desired, the up-down position of region 72 and the source 70 andsensor 34 may be adjusted instead of adjusting the lower stop 44 or 60.

To avoid or minimize channeling of illumination around the float 32 whenit is resting upon stop 44 or 60, it is optionally desirable to coverthe cylindrical member 30 with a light mask which is transparent only inthe region 72.

A typical electronic circuit and signal device is shown in FIG. 9. InFIG. 9, the incoming illumination, represented by the arrow 82, strikesthe photo-transistor 84, causing it to conduct. The output of thephototransistor 84 is connected through an emitter-follower transistor86 to an amplifying transistor 88. The amplifying transistor 88 isbiased by a zener diode 90 and a resistor 92 to prevent spurious signalsfrom activating transistor 88. The output of transistor 88 is channeled,through the center-tap of the primary winding of a transformer 96 to thecollector of a power transistor 98. The signal is also channeled throughthe primary winding and an RC time delay circuit 99 to the base of thetransitor 98. The RC circuit 99 causes the circuit to oscillate,producing ac signals in the secondary winding of the transformer 96which actuate the loud speaker 38.

The audio volume of the apparatus may be adjusted by adjusting therheostat 100 in the collector circuit of transistor 88.

In operation, as the animal 24 breathes the breathing gas, the pressurevaries in the breathing conduit 20 and the sensor conduit 26. Aninhaling by the animal 24 decreases the pressure below atmospheric,causing the float member 32 to rise in the cylindrical tube 30.

When the float member 32 rises in the tube 30, light from theillumination source, such as a light source 70,

penetrates the wall of the tube 30 in the region 72 to stimulate thephoto-sensor 34.

Stimulation of the photo-sensor 34 causes the transistor 88 to conduct,producing an oscillation in the transistor 98 and the transformer 96,producing a tone in the loud speaker 38.

As the animal breathes, the tone from the loud speaker indicates to theveterinarian that the animal 34 continues to breathe. The repetitionrate and duration of the breathing are signaled by the repetition rateand duration of the tones from the loud speaker. The duration andrepetition rate of the tones can be interpreted by the veterinarian totell the depth of anaesthesia of the animal.

In this manner, the breathing of the animal is monitored, and theveterinarian may interrupt the operation to attend to other duties whilelistening to the monitor.

Should the monitor stop, it would indicate that the animal had stoppedbreathing, and the veterinarian should immediately return to the animal.

Although the invention has been described in detail above, it is notintended that the invention should be limited by that description, butonly in accordance with that description in combination with theappended claims.

I claim:

1. A breathing sensor comprising:

I means forming a cylindrical chamber having a substantially verticalaxis, said cylindrical chamber being connected on one end in substantialcommunication with atmospheric pressure and being connected on the otherend to a pressure source whose pressure is a function of the breathingof the user;

said means forming a cylindrical chamber being transparent in at least apredetermined region thereof;

a substantially spherical styrofoam float within said cylindricalchamber, said float having a diameter which is slightly smaller than thediameter of said chamber;

stops at each end of said cylindrical chamber to limit the travel ofsaid float along said chamber, the said stop on the bottom end of saidchamber being positioned to stop said float in said transparent regionof said chamber;

an illumination source, positioned to deliver illumination to one sideof said transparent region, and a photosensor responsive to illuminationtransmitted through said cylindrical chamber, said float beingpositioned, when said float is against said bottom stop, to blockpassage of said illumination to said photo-sensor; and

means connected to be responsive to said photosensor for generating anaudible signal.

2. Apparatus as recited in claim 1 and further comprising a light maskto limit transmission of light through said chamber to a straight linebetween said illumination source and said photo-sensor.

3. In combination with a source of breathing gas and a breathing conduitfor transmitting said breathing gas from said source to an animal;

a substantially circularly cylindrical sensor conduit means open, on afirst end, to said breathing conduit means to cause the pressure insaidsensor conduit means to be a predetermined function of the pressurein said breathing conduit means;

a substantially vertical portion of said sensor conduit means havingstops at opposing ends of said portion;

a substantially spherical styrofoam float'positioned between said stopsand free to move between said stops;

the region of said vertical portion adjacent said lower stop beingtransparent;

a light source positioned to channel light through said transparentportion substantially perpendicular to the axis of said sensor conduitmeans;

a photo-sensor for receiving light from said light source;

electronic means, including an electronic oscillator for producing anaudible signal, connected to be responsive to said electronic means andto light from said light source impinging on said photosensor.

4. Apparatus as recited in claim 3 in which the second end of saidsubstantially vertical portion is in substantial communication with theatmosphere.

5. Apparatus as recited in claim 4 in which said second end of saidsubstantially vertical portion is opened to the atmosphere.

6. Apparatus as recited in claim 4 in which said second end of saidsubstantially vertical portion is opened into a pliable enclosure.

7. Apparatus as recited in claim 2 in which said float weighs betweenthree and twenty grams, and the average clearance between said float andthe inner wall of said chamber is substantially one-half millimeter.

8. Apparatus as recited in claim 7 in which said float weighssubstantially eleven grams.

9. Apparatus as recited in claim 3 in which said float weighs betweenthree and twenty grams, and the average clearance between said float andthe inner wall of said chamber is substantially one-half millimeter.

10. Apparatus as recited in claim 9 in which said float weighssubstantially eleven grams.

1. A breathing sensor comprising: means forming a cylindrical chamberhaving a substantially vertical axis, said cylindrical chamber beingconnected on one end in substantial communication with atmosphericpressure and being connected on the other end to a pressure source whosepressure is a function of the breathing of the user; said means forminga cylindrical chamber being transparent in at least a predeterminedregion thereof; a substantially spherical styrofoam float within saidcylindrical chamber, said float having a diameter which is slightlysmaller than the diameter of said chamber; stops at each end of saidcylindrical chamber to limit the travel of said float along saidchamber, the said stop on the bottom end of said chamber beingpositioned to stop said float in said transparent region of saidchamber; an illumination source, positioned to deliver illumination toone side of said transparent region, and a photosensor responsive toillumination transmitted through said cylindrical chamber, said floatbeing positioned, when said float is against said bottom stop, to blockpassage of said illumination to said photo-sensor; and means connectedto be responsive to Said photo-sensor for generating an audible signal.2. Apparatus as recited in claim 1 and further comprising a light maskto limit transmission of light through said chamber to a straight linebetween said illumination source and said photo-sensor.
 3. Incombination with a source of breathing gas and a breathing conduit fortransmitting said breathing gas from said source to an animal; asubstantially circularly cylindrical sensor conduit means open, on afirst end, to said breathing conduit means to cause the pressure in saidsensor conduit means to be a predetermined function of the pressure insaid breathing conduit means; a substantially vertical portion of saidsensor conduit means having stops at opposing ends of said portion; asubstantially spherical styrofoam float positioned between said stopsand free to move between said stops; the region of said vertical portionadjacent said lower stop being transparent; a light source positioned tochannel light through said transparent portion substantiallyperpendicular to the axis of said sensor conduit means; a photo-sensorfor receiving light from said light source; electronic means, includingan electronic oscillator for producing an audible signal, connected tobe responsive to said electronic means and to light from said lightsource impinging on said photo-sensor.
 4. Apparatus as recited in claim3 in which the second end of said substantially vertical portion is insubstantial communication with the atmosphere.
 5. Apparatus as recitedin claim 4 in which said second end of said substantially verticalportion is opened to the atmosphere.
 6. Apparatus as recited in claim 4in which said second end of said substantially vertical portion isopened into a pliable enclosure.
 7. Apparatus as recited in claim 2 inwhich said float weighs between three and twenty grams, and the averageclearance between said float and the inner wall of said chamber issubstantially one-half millimeter.
 8. Apparatus as recited in claim 7 inwhich said float weighs substantially eleven grams.
 9. Apparatus asrecited in claim 3 in which said float weighs between three and twentygrams, and the average clearance between said float and the inner wallof said chamber is substantially one-half millimeter.
 10. Apparatus asrecited in claim 9 in which said float weighs substantially elevengrams.